The
following is a brief discussions of the various equipment used in continuous distillation:

Distillation column

This is
the main equipment where the separation process described above is carried out.
In general, the distillation column is separated into 3
sections: rectifying (or enriching) section, stripping (or exhausting) section
and feed (or flashing) section. At the rectifying section, the more volatile
component is removed through contacting the rising vapour with the down-flowing
liquid. At the stripping section, the down-flowing liquid is stripped of the more
volatile component by the rising vapour.

The distillation
can be equipped with trays or packings or both. See the Figure
below.

Overhead
condenser

This is a heat exchange equipment for condensing the hot vapour
leaving the top of the distillation column. Either cooling water (e.g. using
shell-and-tube heat exchanger) or air (using fin-fan condensers) can be used
as the cooling medium. In either case, partial or total condensation may be
achieved.

In the case of total condensation (as in the analysis above),
all the vapour is converted into liquid. For partial condensation, there remain
in the vapour state the most volatile components. The condensed liquid is partially
returned to the distillation column as reflux and partially withdrawn as distillate
product. Click here for more
information.

Overhead
accumulator

This is a horizontal (usually) pressure vessel
whereby the condensed vapour is collected.

Pumps

Pumps
can be used for returning the reflux liquid back to the distillation column, or
for pumping out the bottoms product for storage, or for pumping the feed into
the distillation column.

Reboiler

The purpose of the reboiler is to produce the vapour stream
in the distillation column, called the reboiled vapour or the boil-up vapour.
Reboilers can be both external or internal (stab-in). Steam reboilers or fired
reboilers can be used. Fired reboilers typically uses fuel gas or fuel oil or
combination of both. Click here
for more information.

Feed/Bottom Exchanger

The
heat exchanger is used for heat conservation: the hot bottoms stream is used to
heat up the feed stream before it enters the distillation column. As a result
the bottoms product is cooled and then rundown to storage. For better temperature
control of the feed stream, a separate preheater or charge heater (both not shown
in the above diagram) may be used. This is usually located downstream of the feed/bottom
exchanger for final temperature adjustment. Steam may be used for the preheater,
and fuel gas-fuel oil is used for the charge heater.

Charge
Heater / Steam Preheater (not shown in Figure)

This can
be a fuel gas/fuel oil-fired heater or steam-heated exchanger for final temperature
control before the feed enters the column.

NOTE:
Other distillation columns may have slightly different set-ups. The specific equipment
used depends on the types of mixtures to be separated and the complexity of the
operation. Some operations may have more than 1 feed inlet, as well as one or
more sidedraws.